We propose to adapt measures and test a model of factors predicting the implementation of evidence-based practices (EBP) in autism support classrooms. This model incorporates organizational theory with behavior change theory from social psychology. Successful completion of this study will move implementation science towards causal models of implementation. By integrating a validated causal model of behavioral change with organizational variables that have been shown to affect implementation, we will set the stage for future efforts to develop tailored implementation strategies that target the specific determinants of implementation. Most implementation frameworks include variables that describe the organizational context, such as organizational culture, climate and leadership. Many of them also include some individual-level factors that describe characteristics of the practitioners working in these organizations, including psychological factors like attitudes. While there is growing consensus on which organizational variables are most important and how to measure them, implementation scientists have paid less attention to measuring the psychological factors that may be most proximal to implementation, or to the relationships between organizational and psychological factors. When implementation scientists have attempted to measure psychological factors, they have tended to devise their own measures, using strategies that deviate from the well-tested approaches used in social psychology. Our study will rely on our partnership with the School District of Philadelphia, where we provide consultation in EBP to the District's autism support teachers. We will develop measures of psychological factors (intentions, attitudes, perceived norms and self-efficacy) that, according to behavior change theory, will predict the use of evidence-based practice; and then test the feasibility and predictive validity of these measures, combined with validated organizational measures, in predicting the use of four evidence-based practices. Successful completion of this study will lead to two lines of inquiry. First, we will apply for an R01 to examine the generalizability of this approach to different settings. Second, we will develop implementation strategies that are tailored to the specific determinants of EBP implementation. Theory-based interventions targeting specific attitudes, norms and self-efficacy have been highly successful at changing other behaviors, including very complex ones. We believe this approach holds great promise for implementation science as well.